Insert led in my case (analog modulation for normal led)

[Blulaser]

Hi

I need information (if are possible) for insert one ultra bright led in the analog modulation line.

Example insert one led blu in blu analog blanking ,red in red and green in green line.

For you are possible??
thanks
Blu

[ledfreak3d]

sure its possible but the dac is not build to drive leds .
so it may influence the brightnes of your module if u put a led over the modulation line

[mixedgas]

DONT put a led in series with your lines.

That will drop the 0-5V signal anywhere from 3.4 to 1.6 volts, leaving you major issues.

SEE ATTACHED SIMPLE BEGINNERS LED CIRCUIT + NPN transistor.
DO NOT OMIT ANY PARTS

cost, maybe 1.25 per circuit.

build carefully. Adjust R1 upwards for superbright LEDs, may not be very linear without playing with R1 for each color. DO NOT OMIT the 10K base resistor , in order to protect your controller. Do not reduce R1 below 330 Ohms.

STEVE

[andy_con]

i like the sound of leds as a little add on.

i may give this ago

[SideFX]

It some point i noticed my RGB signal range (from a FB3, measured with a scope) was only 0-4V.. I had leds directly connected to them with a 1k resistor, for quite some time actually.. never thought that they could do harm.. when i removed problem was solved!

so you definitely need some sort of buffer like a transistor or opamp to drive a led from the RGB signals.

[dave]

I have done this, but instead of a transistor, I just used a opamp set up as a unity gain buffer.. This has a much higher input impedance than the transistor

[mixedgas]

just sub a MPF102 instead of the 2n2222A, instant 10 gigohms.

Steve

[andy_con]

guys has anyone tried this? does it work ok?

i wana add this to a projector

[cfavreau]

Sounds tight and useful! Thanks for the circuit Steve.

I also heard from a Laserist friend about adding a bi-color LED to the X/Y too. You can use the Bi-Color LED (2 PIN!) or 2 LEDS wired in parallel but one reversed if you don't have a bi-color... use the voltage follower opamp with a current limiting resistor. You will get a mix of the 2 colors because one lights when you get a + swing (above ground) and the other lights when you get a - swing (below ground).

Sounds handy dandy to have visual feedback like that.

I think I will add this to my projector this weekend while I am doing some rewiring anyways.

[dave]

we use 3 leg tri color leds on our projectors for x and y